In Situ Remediation Technologies - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 957

with:

intrinsic permeability (m 2 ) K ig =

η g = dynamic viscosity gas (kg/(m.s)) = (Pa.s).

The dynamic viscosity of soil air is 20 ∗ 10 − 6 (Pa.s), which is 50 times lower
than for water. The soil air permeability is often expressed in cm 2 or in Darcy
(1 Darcy 1 ∗ 10 − 8 cm 2 ). In analogy with the permeability for water the per-

meability of soil gas can vary one order of magnitude at the same location (Hinchee
1994). At low gas permeabilities such as found in clayey and silty soils, applicability
of soil vapour extraction and bioventing is limited.
Some values of the intrinsic permeability of air, K ig , for different soil types are
given in Table 21.1 .

=

Table 21.1 Intrinsic
permeability of air, K ig ,for
different soil types (Norris
et al. 1994 )

Soil type K ig (Darcy)

Coarse sand 100-1000

Medium coarse sand 1-100

Fine sand 0.1-1

Silt/clay <0.1

Electron Acceptors

Especially in biodegradation, the presence and role of electron acceptor donors is
evident, as is demonstrated in Fig. 21.2 (Middeldorp et al. 2002 ). For deep anaero-
bic conditions with CO 2 and sulphate as electron acceptors, reductive dechlorination

Fig. 21.2 Biodegradation rates and dominant degradation mechanisms for different classes of
contaminants under various redox conditions (Middeldorp et al. 2002 )